Gas turbine engines comprise a number of components that are assembled in series and axially. Some of the components are mechanically engaged and fastened together utilizing various types of fasteners and alignment components. For example, in fastening a fan case to a mounting case in a gas turbine engine a number of bolts and pins may be used to both align and maintain an attachment of the two cases. More specifically, a set of pins disposed in pin holes in the fan case and the mounting case maintain alignment and reduce or eliminate radial and circumferential movement. A set of bolts are used to keep the fan case and the mounting case fastened together to prevent separation of the fan case and the mounting case in an axial direction.
Referring to FIG. 1, an existing flange fastening assembly in a gas turbine engine that connects a fan case to a mounting case is shown. A portion of a fan case 10 and a mounting case 12 are shown that are fastened and aligned together using fasteners 14 and a pin 16. The fasteners 14 are disposed through a fan case flange 18 and a mounting case flange 20. The pin 16 is disposed in a pin hole 22 and resists shear forces imparted on the fan case 10 and the mounting case 12 in radial and circumferential directions. It should be noted that the pin 16 and the pin hole 22 are in some circumstances referred to as a shear pin and a shear pin hole respectively. It is highly desirable to make sure that the fan case 10 remains attached to the mounting case 12 during and after a fan blade out (FBO) event in a gas turbine engine (not shown). In an FBO event, a fan blade may completely or partially break off from a fan rotor (not shown). This may likely cause an imbalance in the operation of the fan rotor and generate undesired large forces that could separate the fan case 10 from the mounting case 12 in the axial and/or radial and/or circumferential directions by breaking the fasteners 14 and/or pin(s) 16. Thus, there is a need to retrofit the flange fastening assembly so that during and after an FBO event the fan case is not separated from the mounting case to an extent that would cause a failure in the gas turbine engine.